The project's long term goals are to study neural mechanisms of volition and how neural and cognitive information processing changes in human aging. With functional magnetic resonance imaging (MRI), we will investigate organizing principles of the basal ganglia and cerebral cortex in young and aged human adults. Then we will examine whether aging modifies hypothesized changes in the functional architecture of these brain regions that occurs during repeated sensory stimulation and motor performance, motor skill learning, and conditional motor associations. The first experiment compares relative cerebral blood flow in young and aged adults to develop baseline measures of basal ganglia and cerebral cortical organization. Currently, there remains uncertainty about the precise functional organization of basal ganglia and cerebral cortex in both young or aged adults that occurs during simple sensory and motor tasks. We expect to observe unique activation patterns in a several cortical and basal ganglia regions during presentation of somatic sensory stimuli and performance of simple motor actions. A specific hypothesis of these experiments is that basic brain representation patterns in aging remain similar to those in youth. A prediction of these experiments is the location, size and intensity of activation patterns occurring for somatic sensory stimulation and motor tasks does not differ across aging. A second group of experiments tests the hypothesis that aging diminishes neural adaptation. The experiments examine brain activation occurring during repeated tactile stimulation, movement repetition, formation of visual-motor conditional associations, and acquiring sequential patterns. A specific prediction of these experiments is that aging changes the activation patterns occurring during these "learning" tasks. The experiments will demonstrate the extent to which aging may change the neural representations occurring within the basal ganglia and cerebral cortex during motor learning. Application of the experimental results should enable evaluation of changes occurring in brain physiology not only in human aging, but also in development, neurologic dysfunction, and psychiatric diseases. Understanding the basal ganglia and cerebral cortical basis of learning, visual motor associations, and sequential patterns should enhance rehabilitative strategies for patients with focal brain injury and neurodegenerative and psychiatric diseases.